Numerous modern electronic devices include indicator lights to provide information to a user of the device and to facilitate user interaction with the device. Depending on the application, incandescent bulbs, fluorescent bulbs, or clustered or single light emitting diodes (LEDs) may be used as indicator lights. However, common approaches to indicator lights may not provide satisfactory performance when there is only limited power available to an indicator that needs to be visible in daylight.
One familiar design uses one or more fluorescent or incandescent bulbs positioned behind a window or transparent diffusing overlay printed with indicator graphics. This design is commonly used in gasoline dispensers, xe2x80x9cgas pumpsxe2x80x9d in which, for example, the price for each type of gasoline is shown in a display that is backlighted with incandescent bulbs. Another common example is the lighted status indicators, commonly called xe2x80x9cidiot lights,xe2x80x9d in automotive instrument clusters. Graphics on many switches and buttons in cars also may have incandescent backlighting. However, these approaches may not be suitable when available power is limited.
Another design makes use of several clustered LEDs with a molded plastic light guide to collect and distribute the light. Alternatively, the light guide may be a simple flat diffuser. Although clustered LEDs have proven useful, for some applications, the cluster may require more power than is available. Also, such a design may require complex tooling to make the light guide and may have the potential for uneven light distribution. Finally even multiple LEDs may not be visible in daylight.
A third option is to use a single LED exposed on a front surface of a device. There are many examples of a single LED design in common electronic products such as telephones, VCRs, stereos, and personal computers. These devices are often meant primarily for indoor use. While using a single LED may satisfy a requirement for low power usage, a single LED may not be visible in daylight, the colors are limited to those available from LED manufacturers, the design precludes backlighted graphics and will not, in general, be weather resistant.
Thus there remains a need for a backlighted indicator for outdoor use, visible in daylight, that has low power requirements.
A single LED combined with a dark-colored reflective cavity, a diffusing graphic overlay, and a dark tinted window, provides a backlighted indicator with low power requirements. The design exhibits high visual contrast between on and off conditions, giving daylight visibility. The diffusing overlay and the window are nested and individually attached to a housing with adhesives, thus providing a double barrier against liquid penetration. Thus, the indicator can be used outdoors and under conditions of limited power. For example, the indicator may be part of a customer terminal mounted outdoors at retail establishments, such as gasoline stations.